/* @flow */

import config from '../config'
import VNode, {createEmptyVNode} from './vnode'
import {createComponent} from './create-component'
import {traverse} from '../observer/traverse'

import {
  warn,
  isDef,
  isUndef,
  isTrue,
  isObject,
  isPrimitive,
  resolveAsset
} from '../util/index'

import {
  normalizeChildren,
  simpleNormalizeChildren
} from './helpers/index'

const SIMPLE_NORMALIZE = 1
const ALWAYS_NORMALIZE = 2

// wrapper function for providing a more flexible interface
// without getting yelled at by flow
export function createElement(
  context: Component,
  tag: any,
  data: any,
  children: any,
  normalizationType: any,
  alwaysNormalize: boolean
): VNode | Array<VNode> {
  if (Array.isArray(data) || isPrimitive(data)) {
    normalizationType = children
    children = data
    data = undefined
  }
  if (isTrue(alwaysNormalize)) {
    normalizationType = ALWAYS_NORMALIZE
  }
  return _createElement(context, tag, data, children, normalizationType)
}

export function _createElement(
  context: Component,
  tag

? : string | Class < Component > | Function | Object,
  data ? : VNodeData,
  children ? : any,
  normalizationType ? : number
):
VNode | Array < VNode > {
  if(isDef(data) && isDef((data: any).__ob__
))
{
  process.env.NODE_ENV !== 'production' && warn(
    `Avoid using observed data object as vnode data: ${JSON.stringify(data)}\n` +
    'Always create fresh vnode data objects in each render!',
    context
  )
  return createEmptyVNode()
}
// object syntax in v-bind
if (isDef(data) && isDef(data.is)) {
  tag = data.is
}
if (!tag) {
  // in case of component :is set to falsy value
  return createEmptyVNode()
}
// warn against non-primitive key
if (process.env.NODE_ENV !== 'production' &&
  isDef(data) && isDef(data.key) && !isPrimitive(data.key)
) {
  if (!__WEEX__ || !('@binding' in data.key)) {
    warn(
      'Avoid using non-primitive value as key, ' +
      'use string/number value instead.',
      context
    )
  }
}
// support single function children as default scoped slot
if (Array.isArray(children) &&
  typeof children[0] === 'function'
) {
  data = data || {}
  data.scopedSlots = {default: children[0]}
  children.length = 0
}
if (normalizationType === ALWAYS_NORMALIZE) {
  children = normalizeChildren(children)
} else if (normalizationType === SIMPLE_NORMALIZE) {
  children = simpleNormalizeChildren(children)
}
let vnode, ns
if (typeof tag === 'string') {
  let Ctor
  ns = (context.$vnode && context.$vnode.ns) || config.getTagNamespace(tag)
  if (config.isReservedTag(tag)) {
    // platform built-in elements
    if (process.env.NODE_ENV !== 'production' && isDef(data) && isDef(data.nativeOn)) {
      warn(
        `The .native modifier for v-on is only valid on components but it was used on <${tag}>.`,
        context
      )
    }
    vnode = new VNode(
      config.parsePlatformTagName(tag), data, children,
      undefined, undefined, context
    )
  } else if ((!data || !data.pre) && isDef(Ctor = resolveAsset(context.$options, 'components', tag))) {
    // component
    vnode = createComponent(Ctor, data, context, children, tag)
  } else {
    // unknown or unlisted namespaced elements
    // check at runtime because it may get assigned a namespace when its
    // parent normalizes children
    vnode = new VNode(
      tag, data, children,
      undefined, undefined, context
    )
  }
} else {
  // direct component options / constructor
  vnode = createComponent(tag, data, context, children)
}
if (Array.isArray(vnode)) {
  return vnode
} else if (isDef(vnode)) {
  if (isDef(ns)) applyNS(vnode, ns)
  if (isDef(data)) registerDeepBindings(data)
  return vnode
} else {
  return createEmptyVNode()
}
}

function applyNS(vnode, ns, force) {
  vnode.ns = ns
  if (vnode.tag === 'foreignObject') {
    // use default namespace inside foreignObject
    ns = undefined
    force = true
  }
  if (isDef(vnode.children)) {
    for (let i = 0, l = vnode.children.length; i < l; i++) {
      const child = vnode.children[i]
      if (isDef(child.tag) && (
        isUndef(child.ns) || (isTrue(force) && child.tag !== 'svg'))) {
        applyNS(child, ns, force)
      }
    }
  }
}

// ref #5318
// necessary to ensure parent re-render when deep bindings like :style and
// :class are used on slot nodes
function registerDeepBindings(data) {
  if (isObject(data.style)) {
    traverse(data.style)
  }
  if (isObject(data.class)) {
    traverse(data.class)
  }
}
